Pennsylvania's tough new voter identification law is on trial as civil libertarians seek to have the statute declared unconstitutional.

The trial that began Monday before Commonwealth Court Bernard McGinley will examine a challenge by several voting-rights groups that say the state cannot has not done enough to ensure all eligible voters can get the necessary ID. State officials insist that they've taken all reasonable steps.

The Republican-backed law, one of the strictest in the nation, requires voters to provide certain photo ID before they can cast ballots. Although Gov. Tom Corbett signed it in March 2012, courts have blocked enforcement since before last year's presidential election.

Critics said the law is a Republican attempt to discourage voting by Democratic-leaning voters, while supporters say it would discourage voter fraud.